Vacuum spark advance cutoff

ABSTRACT

A mechanical device is inserted between the engine distributor servo actuator and the carburetor spark port comprising an atmospheric air bleed controlled by changes in vacuum level in the spark port during vehicle accelerations from an engine idle speed or any speed without spark port vacuum; the bleed immediately moving the spark timing to a maximum retard position. The device consists of a valve to open and close an air vent in response to a power actuator connected to the spark port and having an orifice interconnecting abutting chambers of the power device.

United States Patent 1 1111 3,712,279 Vartanian 1 1 Jan. 23, 1973 i751Inventor: inciii'd Divan/1111511, iia'rfidfn.

15 1 VACUUM SPARK ADVANCE CUTOFF 3,476,094 11/1969 Rucins et a1..123/117 A Primary Examiner-Laurence M. Goodridge AssistantExaminer-Cort Flint AttrneyJohn R. Faulkner and Robert E. McCollum Mich.

[73] Assignee: Ford Motor Company, Dearborn,

57 ABSTRACT [22] Filed: Dec. 2, 1970 A mechanical device is insertedbetween the engine distributor servo actuator and the carburetor spark[2H App! 94362 port comprising an atmospheric air bleed controlled bychanges in vacuum level in the spark port during [52] US. Cl. ..123/ 117A vehicle accelerations from an engine idle speed or any [51] Int. Cl..F02p 5/06 speed i h p r p vacuum; the bleed [58] Field of Search..123/1l7 mediately moving the spark timing to a maximum retardposition. The device consists of a valve to open 5 Ref e Cited and closean air vent in response to a power actuator connected to the spark portand having an orifice in- UNITED STATES PATENTS terconnecting abuttingchambers of the power device.

3,606,871 9 1971 Gropp et a1 ....123/117 A 2,361,271 10/1944 Colvin.123/l17 A A a 2,650,581 9/1953 Short ..123/1 17 A 5 Claims, 1 DrawingFigure 3,289,659 12/1966 Koole ..l23/117 A 3,431,897 3/1969 Eltinge..l23/117 A l J0 Z4- 74- 5a 76 t 42 J4 /2 O 4 JG /6 4 J2/66 O 1 O 636PATENTEDJANZB 1915 3,712,279

ATTORNEYS VACUUM SPARK ADVANCE CUTOFF This invention relates, ingeneral, to a device that aids in the reduction of exhaust emissionpollutants from an internal combustion engine. More specifically, itrelates to a mechanical spark timing control device that eliminatescarburetor spark port vacuum to the distributor during vehicleaccelerations from essentially idle speed conditions to minimize theoutput of undesirable elements.

Most present day motor vehicles have some sort of a vacuum servoautomatically controlling the advance or retard setting of the enginedistributor breaker plate as a function of carburetor spark port vacuumto provide good engine performance as well as fuel economy during thedifferent operating conditions of the engine. These vacuum servos, intheir simplest forms, generally consists of a housing divided intoatmospheric pressure and vacuum chambersby a flexible diaphragmconnected to the distributor breaker plate. The diaphragm and breakerplate are normally spring biased to the lowest advance or retard sparktiming setting, and carburetor spark port vacuum normally urges thediaphragm in a spark timing advance direction upon opening of thecarburetor throttle valve in an engine speed increasing direction.

With the above construction, vehicle accelerations from an idle speedcondition cause vacuum at the carburetor spark port to act on the oneside of the servo diaphragm to immediately move the distributor breakerplate to an advanced setting. This provides a longer burning time forthe fuel mixture before the optimum top or near top dead center positionof the piston is attained, generally providing the most desirableoperation. However, this longer time permits a build-up to highercombustion temperatures and pressures, which is undesirable insofar asthe production of oxides of nitrogen and other undesirable elements areconcerned.

It will be seen, therefore, that the conventional spark timing controlsystems may provide goodperformance and fuel economy, but do notnecessarily minimize the output of undesirable exhaust gas elements.

Therefore, it is a primary object of the invention to provide an enginespark timing device that has the advantages of the conventional sparktiming control system while minimizing the disadvantages; by providing adevice that retards the spark timing during vehicle accelerations, todecrease NO X output, while extending burning of the mixture into theexhaust system to reduce the amount of exhaust gas emission of otherundesirable elements.

It is another object of the invention to provide an engine spark timingcontrol system including a device that meets the requirements set outimmediately above, by including a power operated atmospheric pressureair bleed in the vacuum line to the distributor servo to bleed sparkport vacuum during vehicle accelerations.

Other objects, features and advantages of the invention will become moreapparent upon reference to the succeeding detailed description thereof,and to the drawing illustrating a preferred embodiment thereof; whereinthe FIGURE illustrates schematically a crosssectional view of an enginespark timing control apparatus embodying the invention.

The FIGURE shows, schematically, only those portions of an internalcombustion engine that are normally associated with the enginedistributor spark timing setting control; such as, for example, acarburetor 10, a distributor breaker plate 12, a vacuum servo 14 tocontrol the movement of breaker plate 12, and a line 16 connectedbetween the carburetor and vacuum servo to automatically change theengine spark timing setting as a function of changes in engine vacuumspark port setting.

More specifically, carburetor 10 is shown as being of the downdraft typehaving the usual air-fuel induction passage .18 with an atmospheric airinlet 20 at one end and connected to the engine intake manifold 22 atthe opposite end. Passage 1 8 contains the usual fixed area venturi 24and a throttle valve 26. The latter is rotatably mounted on a part ofthe carburetor body across passage 18 in a manner to control the flow ofairfuel mixture into the intake manifold. Fuel would be inducted in theusual manner from a nozzle, not shown, projecting into or adjacentventuri 24, in a known manner.

Throttle valve 26 is shown in its engine idle speed position essentiallyclosing induction passage 18, and is rotatable to a nearly verticalposition essentially unblocking passage 18. A spark port 28 is providedat a point just above the idle position of throttle valve 26, to betraversed by the throttle valve during its opening or part throttlemovements. This will change the vacuum level in spark port 28 as afunction of the rotative position of the throttle valve, the spark portreflecting essentially atmospheric pressure in the air inlet 20 uponclosure of the throttle valve.

As stated previously, the distributor, not shown, includes a breakerplate 12 that is pivotally mounted at 30 on a stationary portion of thedistributor, and movable with respect to cam 32. The latter has sixpeaks 34 corresponding to the number of engine cylinders. Each peakcooperates with the follower 36 of a breaker point set 38 to make andbreak the spark connection in a known manner for each one-sixth, in thiscase, rotation of cam 32. Pivotal movement of breaker plate 12 in acounterclockwise sparkretard setting direction,or in a clockwise sparkadvance setting, is provided by an actuator 40 slidably extending fromvacuum servo l4.

Servo 14 may be of a conventional construction. It has a hollow housing42 whose interior is divided into an atmospheric pressure chamber 44 anda vacuum chamber 46 by an annular flexible diaphragm 48. The diaphragmis fixedly secured to actuator 40, and is biased in a rightward retarddirection by a compression spring50. Chamber 44 has an atmospheric orambient pressure vent, not shown, while the chamber 46 is connected toline 16.

During engine-off and other operating conditions to be described,atmospheric pressure exists on both sides of the diaphragm 48,permitting spring 50 to force the actuator 40 to the lowest advance orav retard setting position. Application of vacuum to chamber 46 movesdiaphragm 48 and actuator 40 toward the left to an engine spark timingadvance position, by degree, as a function of the change in vacuumlevel.

Turning now to the invention, an air bleed device 52 is located in line16 between servo l4 and spark port 28. The device 52 includes a valvebody 54 defining a three passage fluid chamber 56. Passage 58 is a ventand connects to atmospheric pressure. Passage 60 is connected to servoline 16, and passage 62 is connected through an orifice 64 to spark port28. Orifice 64 does not materially affect flow, but is merely to preventintermittent momentary pressure fluctuations from influencing upstreampressure levels.

A valve member 66 is sealingly mounted to slide through a wall of valvebody 54, as shown. It alternately seats against passage 58 to block it,or is moved to the position shown, to bleed air into line 60. The upperend of valve 66 is fixed to an annular flexible diaphragm 68, whichdivides a hollow housing 70 into two fluid chambers 72 and 74. Chamber72 is connected by a passage 75 to spark port 28 on the upstream side oforifice 64. Chamber 74 is closed, and connected to chamber 72 by ametering orifice or flow restricion 76. A spring 78 normally biasesdiaphragm 68 and valve 66 to close bleed passage 58.

In operation, at engine start up, both chambers 72 and 74 of device 52,and both sides of the servo 14 are at atmospheric pressure. Accordingly,spring 78 biases valve 66 to close bleed 58, and the distributor breakerplate 12 is rotated to its maximum retard spark timing position.

The condition described above also holds for engine idle speed position,in that the pressure in spark port 28 is essentially atmospheric, orthat in the air inlet portion 20.

Assume now that the vehicle accelerates, throttle valve 26 rotatingcounterclockwise. Immediately, spark port 28 is subject to vacuum in theintake manifold 22. Though low, the vacuum acting through chamber 72permits the atmospheric pressure in chamber 74 to compress spring 78 andmove valve 66 to open bleed passage 58. This maintains passage 60 atatmospheric pressure and, therefore, servo chamber 46. Accordingly, thebreaker plate 12 is maintained in the maximum engine spark retardposition. As the acceleration of the vehicle proceeds, the build-up invacuum at the spark port 28 will be reflected in chamber 74 by way ofthe orifice 76. Once the pressure in the two chambers 72 and 74 arebalanced, the spring 78 will close the bleed passage 58 and permitvacuum to be applied to the servo chamber 46 via passage 62. As statedpreviously, the orifice 64 at this time does not interfere with the flowof vacuum to passage 60 in chamber 46. Accordingly, the breaker platewill be rotated slowly in a spark timing advance direction as a functionof the degree of throttle rotation.

If the throttle valve is now suddenly moved to a closed position,indicating a decelerating operation, the atmospheric pressure at sparkport 28 and chamber 72 will be ineffective to move the bleed valve 66from the position closing bleed passage '58. Accordingly, the quicklyincreasing pressure in spark port 28 will be reflected directly throughline 62 311C160 to the servo chamber 46 and move the breaker platetowards the maximum spark retard position. It will be understood, ofcourse, that the lowering of the setting will correspond to the degreeof closing of the throttle valve; i.e., if the throttle valve is onlypartially moved to a closed position, the bleed of vacuum at the sparkport will slowly lower the spark port setting.

Subsequent acceleration of the vehicle will again subject spark port 28to a vacuum and cause an unseating of the bleed valve 66. Therefore, theengine spark timing setting at this time will depend upon whether or notthe pressure level at the spark port and chamber 72 is lower than thatpresent in chamber 74. If so, the bleed valve 66 will unseat andimmediately condition the breaker plate for a maximum retard setting. Ifnot, the closing of the bleed valve will reflect the spark port vacuumto the servo chamber 46 and position the breaker plate accordingly.

From the above it will be seen that the invention conditions the enginespark timing for a maximum retard setting .at engine idle speedoperation and maintains that retard setting during vehicle accelerationsfrom idle speed or from a condition of no spark vacuum at a particularspeed. It will also be seen that the device permits normal advance ofthe spark timing after a predetermined interval of time determined bythe orifice between the chambers of the air bleed control device, andthat deceleration spark timing is controlled as a function of themovement of the throttle valve to slowly move the breaker plate towardsa maximum retard position.

I claim:

1. A spark timing control system comprising, an engine carburetor havingan induction passage containing a spark port located just above the idlespeed position of a throttle valve controlling flow through the passageand subject to the depression in the carburetor as a function of themovement of the throttle valve from its idle speed position, an enginedistributor having a breaker plate pivotally movable in oppositedirections to advance and retard the spark timing, vacuum controlledservo means connected to the breaker plate for moving the same, andmeans for controlling advance and retard of the timing solely as afunction of spark port vacuum level changes, the latter means includingconduit means connecting the vacuum at the spark port to the servomeans, flow rate control means in the conduit means between said sparkport and servo means to control the rate of change of application ofvacuum from said spark port to said servo means for effecting variablemovement of said breaker plate from a maximum retard setting at closedthrottle valve idle speed position to a maximum advance setting at highspark port off-idle vacuum levels, and an air bleed means operable inresponse to a drop in the pressure level at the spark port below itsprevious level in response to light accelerative movement of thethrottle valve to momentarily bleed air to the servo means to move thebreaker plate towards a maximum retard setting and subsequently closethe bleed to advance the breaker plate setting upon increase in vacuumlevel at said spark port.

2. A control system as in claim 1, including-second servo means operablyconnected to said bleed means and to the vacuum at said spark port to bemovable thereby.

3. A control system as in claim 1, said bleed means including a valvemeans operably opened by means movable by vacuum connected thereto fromsaid spark port.

4. A control system as in claim 3, said power means including a vacuumservo having a flexible diaphragm dividing said servo into two pressurechambers connected by an orifice, means connecting said diaphragm tosaid bleed valve means, spring means biasing said bleed valve means to aclosed bleed position, and other conduit means connecting one of saidchambers to said spark port.

5. A spark timing control system comprising, an engine carburetor havingan induction passage containing a spark port located above the idlespeed position of a throttle valve controlling flow through the passageand subject to the depression in the carburetor as a function of themovement of the throttle valve from its idle speed position, an enginedistributor having a breaker plate pivotally movable in oppositedirections to advance and retard the spark timing, vacuum controlledservo means connected to said breaker plate for moving the same, andmeans for controlling advance and retard of the timing solely as afunction of spark port vacuum level changes, the latter means includingconduit means connecting said spark port and servo means, flow ratecontrol means in the conduit means "said second servo means including ahousing containing a movable spring biased diaphragm connected to saidvalve means and dividing said housing into a pair of chambers withorifice means therebetween, and other conduit means connecting one ofsaid chambers to said spark port, the orifice means providing subsequentequalization of the pressure levels in the chambers after opening of thebleed valve to permit closing of the valve and an advance movement ofthe breaker plate.

1. A spark timing control system comprising, an engine carburetor having an induction passage containing a spark port located just above the idle speed position of a throttle valve controlling flow through the passage and subject to the depression in the carburetor as a function of the movement of the throttle valve from its idle speed position, an engine distributor having a breaker plate pivotally movable in opposite directions to advance and retard the spark timing, vacuum controlled servo means connected to the breaker plate for moving the same, and means for controlling advance and retard of the timing solely as a function of spark port vacuum level changes, the latter means including conduit means connecting the vacuum at the spark port to the servo means, flow rate control means in the conduit means between said spark port and servo means to control the rate of change of application of vacuum from said spark port to said servo means for effecting variable movement of said breaker plate from a maximum retard setting at closed throttle valve idle speed position to a maximum advance setting at high spark port off-idle vacuum levels, and an air bleed means operable in response to a drop in the pressure level at the spark port below its previous level in response to light accelerative movement of the throttle valve to momentarily bleed air to the servo means to move the breaker plate towards a maximum retard setting and subsequently close the bleed to advance the breaker plate setting upon increase in vacuum level at said spark port.
 2. A control system as in claim 1, including second servo means operably connected to said bleed means and to the vacuum at said spark port to be movable thereby.
 3. A control system as in claim 1, said bleed means including a valve means operably opened by means movable by vacuum connected thereto from said spark port.
 4. A control system as in claim 3, said power means including a vacuum servo having a flexible diaphragm dividing said servo into two pressure chambers connected by an orifice, means connecting said diaphragm to said bleed valve means, spring means biasing said bleed valve means to a closed bleed position, and other conduit means connecting one of said chambers to said spark port.
 5. A spark timing control system comprising, an engine carburetor having an induction passage containing a spark port located above the idle speed position of a throttle valve controlling flow through the passage and subject to the depression in the carburetor as a function of the movement of the throttle valve from its idle speed position, an engine distributor having a breaker plate pivotally movable in opposite directions to advance and retard the spark timing, vacuum controlled servo means connected to said breaker plate for moving the same, and means for controlling advance and retard of the timing solely as a function of spark port vacuum level changes, the latter means including conduit means connecting said spark port and servo means, flow rate control means in the conduit means between said spark port and servo means to control the rate of change of application of vacuum from said spark port to said servo means, an atmospheric pressure air bleed in said conduit means, valve means movable between positions opening and closing said bleed, second servo means connected to said valve means for moving the same and operable at times by and in response to decreases in said spark port pressure level from a previous higher pressure level to open the bleed and thereby momentarily condition the setting of said breaker plate for maximum spark timing retard, said second servo means including a housing containing a movable spring biased diaphragm connected to said valve means and dividing said housing into a pair of chambers with orifice means therebetween, and other conduit means connecting one of said chambers to said spark port, the orifice means providing subsequent equalization of the pressure levels in the chambers after opening of the bleed valve to permit closing of the valve and an advance movement of the breaker plate. 